1. Field of the Invention
The present invention generally relates to a dielectric resonator arrangement, and more particularly, to a dielectric resonator device constructed by forming a plurality of resonator electrodes on a dielectric substrate or dielectric block.
2. Description of Related Art
Conventionally, there have been employed a multi-stage dielectric resonator device constituted by forming a plurality of resonance electrodes (inner electrodes) within a dielectric block, and a ground electrode over the outer face of said dielectric block, and a strip-line type multi-stage resonator device having a plurality of resonance electrodes formed on the surface of a dielectric substrate, and a ground electrode formed on a confronting surface of said dielectric substrate, for example, as a band-pass filter, etc. in a microwave band region.
In the dielectric resonator device having a plurality of inner electrodes formed within the dielectric block, coupling bores or holes are formed to achieve coupling among respective resonators for setting of the amount of coupling by the size of such coupling bores. However, in this type of the resonator device in which the coupling bores are to be provided, not only is the productivity low in the manufacture of the device, but it has been difficult to adjust the coupling amount properly.
Therefore, it has been considered to control resonator characteristics by adjusting the range over which the inner electrodes are formed as shown in FIG. 4(A), which is a top plan view of a conventional dielectric resonator device, and FIG. 4(B) representing a side sectional view taken along the line IV(B)--IV(B) in FIG. 4(A).
In FIGS. 4(A) and 4(B), the known resonator device, for example, in the form of a symmetrical 4 stage band-pass filter, includes a dielectric block 1' with four through-holes formed therein, and inner electrodes 2a', 2b', 2c' and 2d' formed on the inner peripheral surfaces of said through-holes. The dielectric resonator device as referred to above may be represented by an equivalent circuit as shown in FIG. 5, in which R1, R2, R3 and R4 denote the resonators formed by the inner electrodes 2a', 2b', 2c' and 2d' as shown in FIGS. 4(A) and 4(B), with symbols K1 and K2 representing the coupling amounts between the respective neighboring resonators. In the dielectric resonator device having the construction as illustrated in FIGS. 4(A) and 4(B), for example, the resonance frequency of the resonator R2 is determined by a length L2' of the inner electrode 2b' at a second stage, while the coupling amount K2 is determined by a length S2' of a region in which the inner electrode is not formed, and an interval P2' between the inner electrodes 2b'-2c'.
When a filter is to be designed in which the relations represented by f1&gt;f2 and K1&gt;K2 are true on the assumption that the dielectric resonator device shown in FIGS. 4(A) and 4(B) is constructed as the symmetrical 4 stage band-pass filter, and the resonance frequencies of the resonators R1 and R4 are represented by f1, and those of the resonators R2 and R3, by f2, the procedure for the design will be as follows.
(i) To determine the length L2' of the inner electrodes 2b' and 2c' according to the resonance frequencies f2. PA0 (ii) To determine the length S2' of the region without the inner electrode and/or the intervals P2' between the inner electrodes 2b-2c' according to the coupling amount K2, with consequent determination of the axial length L thereby. PA0 (iii) To determine the length L1' of the inner electrodes 2a' and 2b' according to the resonance frequency f1, with consequent determination of S1'. PA0 (iv) To determine the interval P1' between the inner electrodes 2a'-2b' and 2c'-2d' according to the coupling amount K1.
Although the symmetrical 4 stage band-pass filter may be designed in the manner as described above, since the interval P1' and P2' between the inner electrodes are not constant according to the filter characteristics aimed at, different metal molds are required for each kind of filter, thus resulting in high manufacturing cost.